Water-blocking in optical-fiber buffer tubes and fiber optic cables typically has been accomplished by using petroleum-based filling gels (e.g., grease). By completely filling all of the free space inside a buffer tube that contains an optical fiber or optical-fiber bundle, the filling gel blocks the ingress of water into the fiber optic cable.
Moreover, being a thixotropic material, the filling gel also tends to mechanically couple the optical fiber(s) to the buffer tube. Such mechanical coupling prevents the optical fiber(s) from retracting inside the buffer tube as the buffer tube is processed during manufacturing, as the cable is installed or otherwise handled in the field, or as the cable is subjected to thermally induced dimensional changes from environmental exposure.
Although relatively effective for controlling cable flooding, the petroleum-based filling gels are inconvenient during cable repair and optical-fiber splicing. The use of such gels requires cleaning the petroleum-based material from optical fibers prior to splicing (and sometimes from equipment and personnel, too), which can be messy and time consuming. Consequently, using conventional filling greases is often undesirable.
Various dry-cable designs have been developed to eliminate filling greases while providing some water-blocking and coupling functionality. In either loose-tube optical-fiber cables or ribbon cables, a totally dry design eliminates the filling gel from the enclosed buffer tubes. In a dry-cable design, for example, filling gel may be replaced by a water-blocking element, such as a tape or a yarn carrying a water-swellable material (e.g., water-swellable powder). Water-swellable powders are dry to the touch and, when bound to a carrier tape or yarn, can be readily removed during field operations (e.g., splicing).
One problem associated with dry-cable designs is that the optical fibers (e.g., optical-fiber ribbon) contained within the cable are often insufficiently coupled to the cable and/or buffer tube enclosing the optical fibers. In the absence of sufficient coupling, the optical fibers can undesirably bunch up inside the cable.
Accordingly, a need exists for an improved way of coupling optical fibers to buffer-tube and/or cable elements.